Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Vbe(base-emitter voltage of BJT) vs temperature

Status
Not open for further replies.

simon0123

Newbie level 6
Newbie level 6
Joined
Jul 6, 2010
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
HK
Activity points
1,361
HI

I would like to ask why Vbe has a negative temperature coefficient? How to prove it ?

thx a lot
 

you can get the detailed derivation from Razavi's book
 

HI
I would like to ask why Vbe has a negative temperature coefficient? How to prove it ?
thx a lot

The electron mobility rises with temperature. Thus, for VBE=const. the emitter produces more electrons and the current increases. On the other hand, for Ic=const (that is the condition to evaluate the Vbe temperature dependence!) a lower Vbe is necessary to produce the same current. Therefore the neg. temp-co for Vbe.
 

The electron mobility rises with temperature..
but i do not think so,
from the formula µ=µo*T^(-3/2), seems mobility decreases with temperature.
 

but i do not think so,
from the formula µ=µo*T^(-3/2), seems mobility decreases with temperature.


Yes, you are right. I didn't use the correct term. It's not the mobility of electrons but rather the ability of the emitter to emit more electrons. This can be verified easily by SHOCKLEY's equation that shows the interdependence between Vbe and Ie with temparature as parameter.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top